Annular seals have been implemented on turbomachinery to prevent leakage of compressible or incompressible fluids such as gases or liquids, respectively. These annular seals generally incorporate a hollow member having a number of depressions formed in its inner surface that is dimensioned to extend around a rotor portion having a relatively smooth surface. In operation, the physical relationship of the rotor surface to the stator surface causes a dynamic resistance to the movement of the fluid through the seal such that a sealing action occurs.
Common types of annular seals include hole pattern (HP) seals and honeycomb (HC) seals. Hole pattern seals generally include depressions in the form of a number of generally round-shaped holes that are formed in the inner surface of its stator portion. Honeycomb seals generally include depressions in the form of generally hexagonal-shaped holes that are formed into a lattice-shaped structure. The inner surface of the hollow member is configured in a spaced apart relation relative to the outer surface of the rotor portion so that no contact is made between the hollow member and rotor portion. In this manner, relatively little wear may be caused to the inner surface of the hollow member or outer surface of the rotor during operation.